This invention relates to an exposure control system for a photographic apparatus, and more particularly, to an improved exposure control system for a fixed focus photographic apparatus of the type having scanning type shutter blades for respectively blocking and unblocking the passage of light through an exposure opening to a film plane and through a photocell opening to a light sensing photocell.
In U.S. Pat. No. 3,942,183, an exposure control system is disclosed for a camera with a housing surrounding a central casting. The housing supports an objective lens assembly in a manner overlying as exposure opening in the casting, providing an optical path through the lens assembly and the exposure opening to an exposure chamber within the camera. The housing and central casting further include overlying sensor openings which in turn overlie a light sensor assembly. The exposure control system includes at least one shutter blade disposed between the housing and casting and having an exposure aperture and a control aperture. The shutter blades are adapted for pivotal and translational motion in response to rotational displacement of a rotatable blade drive member, or walking beam. At the commencement of an exposure cycle, the walking beam is driven from a first limit towards a second limit in response to a bias means. As the walking beam is displaced between its first and second limits, the exposure and control apertures of the shutter blades cooperate to establish a common overlap with the respective exposure and sensor openings, with the percentage of overlap progressively increasing as the walking beam is displaced towards the second limit. In accordance with the disclosure of this referenced patent, an integration network may be coupled to the sensor to identify a point in time when the integral of the light incident upon the sensor has reached a predetermined limit, whereupon the walking beam is returned to its first limit where the exposure and control apertures are non-overlapping with respect to the exposure opening and sensor respectively, thereby blocking the optical path through the exposure opening and terminating the exposure cycle.
The dislcosure of U.S. Pat. No. 3,972,058 is directed to an exposure system having at least one shutter blade driven by a walking beam in a manner similar to the configuration disclosed in U.S. Pat. No. 3,942,183, and wherein further the exposure system is adapted to provide a follow-focus capability for use in conjunction with an artificial light source. As disclosed, with the follow-focus arrangement, the aperture adjustment is coupled to the range finding or focusing system of the camera. The insertion of an artificial light source into a receptacle in the camera housing introduces a stop member in the path of the walking beam in a manner to limit the travel of the walking beam to a third limit point lying between the nominal first and second limits, with the particular third limit point being dependent upon the operator-contolled focus of the camera. This configuration establishes an artificial light mode wherein the disclosed exposure control system is responsive to the insertion of an artificial light source into a receptacle in the camera housing, and to the operator-controlled focus adjustment, to provide a limitation on the maximum effective aperture for the lens and for the sensor. In this mode of operation, the effective lens and sensor apertures progressively increase as the walking beam rotates from the first limit toward the third limit. Upon reaching the third limit, the effective lens and sensor apertures remain constant for the duration of the exposure cycle. While operating in the natural light mode, i.e. without an inserted artificial light source, the walking beam is not affected by the stop member.
While the cameras of the prior art, as exemplified by the above-noted referenced patents, provide effective exposure control systems, those systems are adapted primarily to variable focus cameras and are dependent upon the particular focus condition.
It is an object of the present invention to provide an exposure control system primarily for a fixed focus photographic apparatus.
It is a further object to provide an exposure control system primarily for a fixed focus photographic apparatus characterized by a relatively simple mechanization.
It is another object of the present invention to provide an exposure control system primarily for a fixed focus photographic apparatus having a natural light mode and an artificial light mode of operation, wherein the light integrating network is characterized by a relatively low sensitivity in the natural light mode and a relatively high sensitivity in the artificial light mode.